Optical position assessment apparatus and method

Abstract

A lithographic apparatus comprises a substrate table that supports a substrate having alignment marks on a surface thereof. The apparatus further comprises a frame moveable relative to the substrate to provide for a scanning or stepping mode of operation. An array of projection systems is disposed across the frame for projecting respective patterned beams onto a target portion of the substrate. A plurality of alignment mark detectors are attached to the frame and are moveable with respect to the frame using respective linear drive mechanisms. A position sensor is associated with each alignment mark detector for determining the position of the detector relative to the frame. A control system is responsible for both initial positioning of the detectors above alignment mark patterns on the substrate, and for dynamic alignment of the frame and substrate during a lithographic process.

1. A lithographic apparatus, comprising:
 an illumination system that produces a beam of radiation; 
 a pattern generating device that patterns the beam; 
 a substrate table that supports a substrate, the substrate having alignment marks provided on a surface thereof relative to a plurality of panels having variable or different dimensions, the plurality of panels being supported on the substrate; 
 a frame moveable relative to the substrate; 
 a plurality of projection systems coupled to the frame, wherein the plurality of projection systems are capable of projecting respective portions or copies of the patterned beam onto a target portion of respective ones of the plurality of panels having variable or different dimensions on the substrate; 
 one or more alignment mark detectors coupled to the frame and moveable with respect to the frame, wherein the detectors detect alignment marks by analyzing reflection patterns; and 
 a position sensor associated with each of the one or more alignment mark detectors, wherein the position sensor determines the position of the one or more alignment mark detectors relative to at least one of the frame and the plurality of projection systems. 
 
   
   
     2. The apparatus of  claim 1 , wherein:
 the frame is moveable relative to the substrate along a first axis in a plane substantially parallel to a plane of the substrate; and 
 the one or more alignment mark detectors are movable relative to the frame along a second axis substantially perpendicular to the first axis and in a plane parallel to the plane of the substrate. 
 
   
   
     3. The apparatus of  claim 2 , wherein the one or more alignment mark detectors have a range of movement sufficient to provide coverage of substantially a whole dimension of the substrate in the direction of the second axis. 
   
   
     4. The apparatus of  claim 1 , wherein the one or more alignment mark detectors comprise:
 an illumination system that supplies an alignment beam of radiation; 
 a projection system that projects the alignment beam onto an alignment target portion of the substrate; and 
 a sensor that detects radiation reflected from the substrate. 
 
   
   
     5. The apparatus of  claim 1 , wherein each of the position sensors comprise:
 a laser interferometer. 
 
   
   
     6. The apparatus of  claim 5 , wherein the laser interferometer comprises:
 a reflector or mirror surface fixed relative to the associated alignment mark detector; and 
 a laser and a radiation detector fixed relative to the frame. 
 
   
   
     7. The apparatus of  claim 1 , wherein each of the position sensors comprise:
 a linear grating system. 
 
   
   
     8. The apparatus of  claim 1 , further comprising
 a linear motor associated with each of the one or more alignment mark detectors that provides linear movement of a respective one of the alignment mark detectors relative to the frame. 
 
   
   
     9. The apparatus of  claim 1 , further comprising:
 a controller that controls position of the one or more alignment mark detectors during an exposure period based on at least one of operator inputs and feedback from respective ones of the position sensors, wherein respective position of each of the position sensors moves to correspond in position to the variable or different dimensions of the panels while the substrate is moving along a scanning direction during the exposure period. 
 
   
   
     10. The apparatus of  claim 1 , further comprising:
 an alignment controller that receives an output from the one or more alignment mark detectors and, based on the received signals, adjusts at least one of (i) the position of the substrate relative to the frame, (ii) a scanning speed of the substrate, and (iii) the patterned beam generated by each of the plurality of projection systems. 
 
   
   
     11. The apparatus of  claim 1 , wherein at least five of the one or more alignment mark detectors and respective position sensors are used. 
   
   
     12. A method, comprising:
 during an exposure period determining approximate positions of alignment marks provided proximate to respective ones of a plurality of panels having variable or different dimensions, each of the variable or different dimensioned panels being positioned on a surface of a substrate; and 
 moving one or more alignment mark detectors relative to a frame that is moveable relative to the substrate, wherein the one or more alignment mark detectors are moved to be aligned with respective one or more alignment marks, such that the one or more alignment mark detectors are positioned to correspond to the variable or different dimensioned of panels; 
 determining positions of the one or more alignment mark detectors; and 
 aligning a plurality of projection systems, capable of projecting respective portions or copies of a patterned beam onto a target portion, with respect to respective ones of the plurality of variable or different dimensioned panels on the substrate using the determined positions of the one or more alignment mark detectors. 
 
   
   
     13. The method of  claim 12 , wherein the step of moving one or more alignment mark detectors comprises:
 monitoring an output of one or more detector position sensors to provide detector position feedback, the one or more position sensors being fixed to at least one of the frame and the alignment mark detectors. 
 
   
   
     14. The method of  claim 12 , wherein the step of moving one or more alignment mark detectors comprises:
 applying drive signals to a linear drive mechanism associated with each of the one or more alignment mark detectors. 
 
   
   
     15. The method of  claim 14 , wherein each of the one or more linear drive mechanisms utilize a linear motor. 
   
   
     16. The apparatus of  claim 1 , wherein the frame comprises:
 a base portion; 
 first and second leg portions coupled to opposite sides of the base portion, such that the substrate passes between the first and second leg portions; and 
 a gantry portion, the gantry portion supporting the plurality of projection systems and the one or more alignment mark detectors. 
 
   
   
     17. A lithographic apparatus, comprising:
 an illumination system that produces a beam of radiation; 
 a pattern generating device that patterns the beam; 
 a substrate table that supports a substrate, the substrate having alignment marks provided on a surface thereof relative to a plurality of panels; 
 a frame moveable relative to the substrate; 
 a plurality of projection systems coupled to the frame, wherein the plurality of projection systems are capable of projecting respective portions or copies of the patterned beam onto a target portion of respective ones of the plurality of panels on the substrate; 
 one or more alignment mark detectors coupled to the frame and moveable with respect to the frame, wherein the detectors detect alignment marks by analyzing reflection patterns; 
 a position sensor associated with each of the one or more alignment mark detectors, wherein the position sensor determines the position of the one or more alignment mark detectors relative to at least one of the frame and the plurality of projection systems; and 
 a controller that controls position of the one or more alignment mark detectors during an exposure period based on at least one of operator inputs and feedback from respective ones of the position sensors, wherein respective position of each of the position sensors moves to correspond in position to the various sizes of the panels while the substrate is moving along a scanning direction during the exposure period.